Constant tension unwinding mechanism



Nov. 11, 1958 R LE B. BOWEN, JR 2,859,923

, CONSTANT TENSION UNWINDING MECHANISM Original Filed March 25, 1953 INVENTOR. RICHARD LEBARON BOWEN, JR.

ATTORNEYS United States.

OriginalapplicationMarch 25, 1953, Serial No. 344,520, now Patent N0..2,781,178, dated,F,ebruary.-12,.1957. Divided and thisapplicationNovember16,1956;. Serial No. 622,652

3 Claims. (Cl. 242-'7 5.'47)

This invention relates to a constantweb' tension unwind ing mechanism and-more particularly to amechanism-for maintaining a'constant speed on the web'tensioning mechanism through a variable speed transmission responsive to the change in brakev speed which reacts-tocontrol the speed of the brakingmechanism: g

One of the objects-:of-the present invention is reprevide a constant braking force in a web unwinding mechanism.

Another object-of the present invention is to provide a. constant tension unwinding mechanism which will operate automatically without any attention from an operator.

Still another objectis-theprovision'of a constant tension unwinding mechanism which will inherently permit the accurate duplication of the braking force.

Other objects of the present invention will be pointed out in part and become apparent in part in the following specification and claims.

The present application is a divisional application of my co-pending application Serial No. 344,520 now Patent No. 2,781,178, dated February 12, 1957.

Uniform or constant tension is a prerequisite to uniformity of product in many web processing machines such as textiles, paper, imitation leather, printing and the like. Especially is this true in a web coating machine where the tension in the web effects the nature and thickness of the coating material being applied to the web. Thus, when a supply roll of cloth is placed in a machine, the cloth should be drawn off at a constant speed and at a given tension.

It is common practice to put a mechanical brake on the shaft of the unwinding roll of material. As the diameter of the roll decreases, the speed or linear travel of the cloth or web is maintained constant, but the speed of the unwinding roll :shaft increases in proportion to the decreasing diameter of the roll. If the setting of the mechanical brake is left constant, the tension produced on the web continues to increase in proportion to the increasing speed of the unwinding roll shaft. In such a setup it is necessary to decrease the drag or setting of the mechanical brake on the roll shaft if the tension is to be maintained constant. Past devices have failed to automatically control the drag and thereby regulate the tension accurately in .accordance with the changing tension produced as the supply roll decreases in diameter.

This failure was due in part to the nature of the braking mechanism which consisted of the conventional mechanical arrangement of a brake drum and a shoe provided with a brake lining. The coefiicient of friction between the drum and shoe varied due to the heating caused by the period of operation and the unevenness of the parts and oil and dust accumulation so that the brake slipped and grabbed. There was no way of determining a brake setting for future use since the brake lining continually wore down. The present invention contemplates an oil pump as a brake, the pressure of which is always deter minable for future precise settings.

Patented Nov. 11,1958

V In the drawings:

The single figure is a diagrammatic illustrationof the invention. p

Referring to the drawing, a strip of material 11, is being withdrawn froma beam 12 by means ofa drum 16. Beam 12'is secured to an axle 13' which'has fixedto it bevel gear 14 which meshes with bevel gear 15"fixed to shaft 20 of a continuously variable lspedltrrafismission, generally indicated by reference character 17.] A second shaft21 of variable speed transmission 17 isoperatively connected to a gear pump generally indicated by reference character 35 through a'shaft 36, sprocket 33 fixed, to shaft 36, sprocket 32 fixed to shaft 21 and chain 34. connecting sprockets 32, 33. i v

A reservoir 38 is provided and is operatively connected to gear pump 35 through suction line 37 and discharge line 40. A throttling valve 41 inserted in ,line 40. controls the power exerted by the gear pump,;35. A pressure. gage 42 inserted in line 40 gives a relative indication, of this power.

' The variable speed transmission 17 comprisesa painof parallel shafts 20 and 21 rotatably mounted-in a housing 22. Each shaft 20,21 carries a pairof coneddisks. 23, 24, respectively, forming expansive V, pulleys, which ,are splined'lto'saidshafts. Cloneddisks23, 2,4: are operatively connected throughedge-active belt 25 and, may be simultaneously and oppositely adjusted to. provide variable speed'by the simultaneous adjustment of levers 26 and 27 which are operatively connected to coned disks 23, 24 and pivotally separated by lever 28. The ends of levers 26, 27 are fixed to threaded shaft 30 by means of threaded bearings 31, 31. The rotation of shaft 30 simultaneously and oppositely moves disks 23, 24 on shafts 26, 21, thereby varying the speed of rotation of shaft 20 relative to shaft 21.

Threaded shaft 30 is operatively connected to shaft 62 of a differential gear train generally indicated by reference character 58 by means of sprockets 46, 47 and chain 48, sprocket 47 being fastened to slip clutch 29.

The differential gear train 58 comprises three shafts 60, 61, 62 rotatably mounted in housing 63. Shaft 62 carries a hub 59 which has fixed thereto short shafts 64, 64a that rotatably carry thereon bevel gears 65, 66. These bevel gears are operatively connected to bevel gears 67, 68 rotatably mounted on shaft 62. A spur gear 70 fixed to bevel gear 67 meshes with spur gear 71 fixed to shaft 60. Sprocket 72 fixed to bevel gear 68 is operatively connected by means of chain 73 to sprocket 74 fixed to shaft 61.

It is evident that shafts 60, 61 when rotated in the same direction and at the same speed cause shaft 62 to remain idle. However, any difference in the speeds of shafts 60, 61 when turning in the same direction will cause shaft 62 to rotate, the speed of this rotation being proportional to the difference in the speeds of shafts 60, 61.

Shaft 61 of differential 58 is operatively connected with drum 16 through bevel gear 75 fixed to drum 16 which meshes with bevel gear 76 fixed to shaft 77, on which is fixed sprocket 78 which is connected to sprocket 80 fixed to shaft 61 by means of chain 81. Shaft 60 of differential 58 is operatively connected to shaft 21 of transmission 17 by means of sprockets 82, 83 and chain 84.

Web 11 is withdrawn from beam 12 by means of drum 16 which is driven at a constant speed by means not shown so that web 11 is Withdrawn at a constant linear velocity. When the system is at equilibrium, shafts 60, 61 of differential 58 are revolving at the same speed and shaft 62 is motionless. Shaft 61 is driven at a constant speed by a driving connection with drum 16, which rotates at a constant speed.

As beam 12 unwinds, its diameter decreases and its 3 speed of rotation increases. This increase in speed is immediately transmitted to shaft 60 of differential 58 from shaft 21 of transmission 17. As soon as there is a diflference in speeds between shafts 60, 61 of diflferential 58, shaft 62 commences to rotate, thereby changing the speed of transmission 17 and thus maintaining 'the'speed of shaft 21 constant. Since the speed of shaft 21 isfmaintained constant, thespeed of pump 35 is likewiseJmaim tained constant, and thus the power applied to the web and the tension in the web are also kept constant.

1. In a constant tension web unwinding mechanism, a beam carrying a web, a drum operatively connected to said web and over which the web travels at a constant linear speed, a variable speed transmission provided'with a first shaft, a second shaft, and speed changing mechanism, *said first shaft being arranged for driving engagement with said beam, a gear pump with a' suction and discharge line, a throttling valve in said discharge line, said second shaft being arranged for direct engagement with said gear pump, a differential gear train with three power transmittingielements, the first of said elements being arranged'for drivin'g'engagement with said speed changing mechanism, the second of said elements being arranged for driving engagement with said second shaft, and the third of said elements being arranged for driving engagement with said drum. p '2. In a constant tension unwinding mechanism, a beam carrying a web which is'unwound at a constant linear speed, a variable speed transmission provided with a first shaft,'a second shaft, and a speed changing mechanism, said'first shaft being arranged for'driving engagement with said beam, a gear pump with a suction and discharge line,

a throttling valve in said discharge line, a driving connection between said gear pump and said second shaft, a differential gear train withgthree power transmitting elements, a driving connection between the first of said elements and said speed changing mechanism, a driving connection between the second of said elements and said second shaft, and means for rotating said third element at aconstant speed.- Y

3. In a constant tension unwinding mechanism, a beam carrying a web which is unwound at a constant linear speed, a drum operatively connected to said web over which the web travels at a-cons'tant linear velocity, a variable speed transmission-provided with a first shaft, a second shaft, and a speed changing mechanism, said first shaft being arranged for'driving engagement with said beam, a gear pump comprising a suction line and a discharge line with a throttling valve positioned in said discharge line, a driving connectionfbetween said gear pump and said secondshaft a differential gear train with three rotatable power transmitting elements, a driving connection between ,th'egfirstn'of said elements and said speed changing mechanisms including a slip clutch, ,a driving connection between the second of said elementsand said second shaft, and a driving connection between the third of said elementsand said drum; I

' 1 References Citedin the file ofthis patent UNITED STATES PATENTS "2,392,226 Butterworth et a1'." Jan. 1, 1946 2,631,791 Wheldon Mar. 17, 1953 

